Ecogeographic variation and taxonomic boundaries in Large Treeshrews (Scandentia, Tupaiidae:Tupaia tanaRaffles, 1821) from Southeast Asia

Abstract

The Large Treeshrew, Tupaia tana Raffles, 1821, is a small mammal (~205 g) from Southeast Asia with a complicated taxonomic history. Currently, 15 subspecies are recognized from Borneo, Sumatra, and smaller islands, and many were originally differentiated based on minor pelage differences and small sample sizes. We explored intraspecific variation in T. tana using quantitative osteological data obtained from the hands and skulls of museum specimens. Multivariate analyses reveal extensive overlap among T. tana populations in morphospace, indicating that the majority of currently recognized subspecies are not morphometrically distinct. In contrast, the separation between Bornean and Sumatran populations of T. tana is sufficient to recognize them as different subspecies. Comparisons of Bornean specimens to those on small, offshore islands reveal that the latter average smaller body size. This pattern is inconsistent with Foster’s island rule, which predicts that island populations of small mammals (< 5 kg) will average larger body size relative to mainland forms. A similar lack of support for ecogeographic rules has been noted in T. glis (Diard, 1820), suggesting that these “rules” are poor predictors of geographic variation in treeshrews.

Recent and rapid ecogeographical rule reversals in Northern Treeshrews

“…Although previous studies have found that Bergmann’s rule or the island rule are inverted or inapplicable in other treeshrew species 14 , 36 , 37 , ours is the first to demonstrate an interaction between these two rules in this group of mammals, and one of the very few to show this in any mammalian species 11 , 12 , 38 . Mainland individuals of T. belangeri display a clear reversal of Bergmann’s rule, whereas island individuals increase in size with latitude as expected (Figs.…”

“…Our work highlights the crucial ongoing role of museums in the documentation, prediction, and mitigation of anthropogenic impacts on biodiversity. S5) 14,36,[49][50][51][52][53][54] from 839 adult (those with fully erupted permanent dentition 55 ) museum specimens of Tupaia belangeri (Supplementary Appendix) using Mitutoyo digital calipers that read to 0.01 mm. Because of occasional broken or damaged skulls, we were unable to record all measurements for all individuals.…”

“…EJS recorded 22 craniomandibular measurements (Supplementary Table S5 ) 14 , 36 , 49 – 54 from 839 adult (those with fully erupted permanent dentition 55 ) museum specimens of Tupaia belangeri (Supplementary Appendix) using Mitutoyo digital calipers that read to 0.01 mm. Because of occasional broken or damaged skulls, we were unable to record all measurements for all individuals.…”